Morphology and rheological behaviour of Yarrowia lipolytica: Impact of dissolved oxygen level on cell growth and lipid composition

Yarrowia lipolytica was investigated as potential ascomycetes yeast for higher lipid productivity. Moreover, lipogenesis seems to be very sensitive to oxygen variation and to achieve efficient microbial conversion of crude glycerol into energetic molecules (single cell oils, SCO) is a real challenge in the bioprocess. Dissolved oxygen (DO) was selected as a key parameter for translating results from shake flask to large scale for a successful bioprocess. Lipid production under different oxygenation rates was carried out to identify the ideal scenario required for higher accumulation rate. A combination of metabolomic, morphological and rheological profiling was investigated in the presence of crude glycerol as a carbon substrate. Results showed that cells require a dissolved oxygen concentration of 30% to achieve the highest lipid production of 44.8 +/- 1.2% (w/w). The increase or decrease of oxygen level might affect the lipid content. However, cells exhibited the same rheological behaviour and presented unimodal distribution despite the oxygen variation. Furthermore, broth rheology was ultimately dependent on nutrient limitation and aeration. The variation of oxygen level (i.e. volumetric oxygen transfer coefficient (K(L)a) and oxygen uptake rate (OUR)) affects the biomass concentration, lipid accumulation and composition. These parameters played a crucial role in determining bioprocess performance.